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60                           METALLUHGY OF IROJST AND STEEL.
:• I have commented on the necessity of invoking something beside the oxidizing influence of carbonic acid upon iron to explain the
. beginning of the carbon impregnation, but the question is puzzling and difficult to investigate. The subject is of great importance, as it is known that carbonic oxide alone is unable to remove the last traces of oxygen from iron oxide, this office being performed by deposited carbon in the lower region of the blastfurnace, and it
.is also known that carbon deposition ceases at about 600° C. and
•that carbonic acid (CCX) then acts upon and dissolves carbon, so that in the lower and hotter portions of the furnace there is no carbo-n deposit except what is associated with the iron, waiting for
» a chance to" unite with it as carbide.         ...'.-
Howe* has reviewed the work of Bell and others very thoroughly
;in respect to. carbon impregnation, and concludes thus: ;;: "The exact nature of the reactions is not known.   Metals which
'.like .iron are reduced by carbonic oxide, but which unlike it are not
, oxidized by this gas or by carbonic acid, do not induce carbon deposition as far as known : this suggests that It is connected with the oxidation of iron by one or both of these gases by reactions like the following : ...
rather than to mere dissociation of carbonic oxide, thus :
which may be the resultant of either of these two reactions .:"
The chemical phenomena .of a blast furnace have been represented graphically by Bell, and also in a book by Prof. Eobt. H. •Bicha'rds for use in 'the Massachusetts, Institute of Technology, but no attempt has been made to show them with quantitative accuracy. I believe it is possible to map out the reactions, after assuming certain conditions. I have been assisted in this task by Mr. John
• '.    * Metallurgy, •$. 122.     :      .                  '                        •.<.-.•